Wow, a necro thread back from the death?
My idea is this:
You send an amount x,you tell me if you want to bet high or low, I check the transation tx numbers and sum the last 11 numbers of your transation id, if you win I send you double.
That is provably fair, and I bet it's not a new method, isn't it?
Sorry this is not provably fair, I only do bets recorded with camtasia and then uploaded to youtube